The present invention relates generally to testing of data transmission circuits of digital telecommunications systems and testing of protocols associated with digital data carried on such circuits. More particularly, the invention relates to systems and methods permitting both physical and logical testing of data circuits in one test system and enabling diagnosis of probable cause of faults based on results of both physical and logical tests.
Digital data is transmitted over complex telecommunications systems operated by carriers which provide circuits coupled to individual customer's facilities. At their facilities, customers connect data terminals and other equipment at various stations to permit the transmission of data to geographically separated points. When a problem is experienced in the transmission of data from station A to station Z, from station Z to station A, or in both directions between stations A and Z, the problem can be caused by a physical fault in the transmission circuit, a logical fault in the protocols used in the transmission of data, or possibly by a combination of physical and logical faults.
This differentiation between physical and logical faults should be carefully noted. A physical fault represents a physical inability of a circuit to properly transmit data between the desired stations. A logical fault represents a defect relating to the protocol used to control the transmission of data between the desired stations. A "protocol" is a defined set of rules or coding format for transmission of information between desired stations. Many forms of standard and specialized protocols typically address the same functions, including data framing, error detection, error correction, multi-point polling, addressing and flow control. If the protocol is not properly implemented and interpreted data cannot be accurately transmitted over a digital telecommunications network. Thus, while a transmission fault will physically interfere with transmission of data, a protocol fault will also interfere with data transmission, even in the absence of a physical circuit fault.
Typically, when a customer experiences a problem in transmitting data between two stations, the customer has had no effective way of determining whether there is a physical transmission problem on the carrier-supplied circuit, or whether there is a protocol processing problem at the sending station or receiving station, for example. As a result, the circuit could remain inoperative while the customer complained to the carrier and the carrier carried out physical transmission testing of the circuit. Then, if the carrier found no fault, the customer could be forced to contact the vendors of equipment used at different stations which might be involved in causing a protocol fault. Additional time could be consumed while the equipment vendors addressed the source of the problem, so that the fault could be finally located and fixed. Thus, there has been a continuing need for practical and effective means for customers to locate faults affecting the transmission of data between stations, without dependence on carriers, equipment vendors, or both.
At the carrier level, there are test systems available which permit effective physical testing of digital data transmission circuits. A prime example is the REACT 2000 Operations Support System developed and marketed by Hekimian Laboratories, Inc., the assignee of the present inventor. These systems are used by technical personnel of the carrier to identify transmission faults caused by defects in the transmission circuits. At the present time, however, these personnel have typically not been experienced or qualified in the identification of protocol faults, since such faults do not basically relate to the transmission system provided by the carrier, but relate instead to the customer's use of the circuit provided by the carrier.
With respect to protocol testing, there is protocol test equipment available which permits effective testing of respective digital protocols associated with the transmission of data between stations over a particular transmission circuit. The technical personnel qualified in the use of such protocol test equipment are normally different individuals than those qualified in physical transmission testing. As a result, two different technicians using two different pieces of test equipment are commonly needed to locate faults. In addition, the respective tests are typically carried out at two different locations, i.e., transmission tests at the carrier's facility and protocol tests at the customer's facility.
Certain patents provide background to the present invention. U.S. Pat. No. 4,792,753 describes a local area network protocol analyzer which performs statistical analysis of the traffic loading of the network under test. The generation and display of certain message traffic characteristics are addressed. U.S. Pat. No. 3,826,908 describes a prior art type data telecommunications analyzer for performing protocol analysis on a stand-alone basis at a customer site. U.S. Pat. No. 4,750,175 describes a data processing network test system for diagnosing malfunctions in a network, network components or software through protocol analysis. Analysis is performed by a remote central computer receiving modified data packets from test computers at local data processing sites which receive data packets detected at probe locations at the local sites. The data packets are detected and modified before transmission to the central computer to maintain message privacy during protocol analysis. U.S. Pat. Nos. 4,817,092; 4,873,687 and 4,881,230 describe the use of expert systems for detecting and analyzing equipment failure in a multiplex digital communication system and alerting the operator as to remedial action if corrective action cannot be implemented automatically.
While these prior patents, and certain prior equipment which will be referred to in describing the invention, represent available approaches to fault identification, they have not provided solutions to the problems discussed above. Specifically, no solution is provided to enable analysis of transmission and protocol problems on an integrated, customer-accessible basis, and the additional benefits thereby made possible in accordance with the present invention are not suggested.
So far as the applicant is aware, there has not been available any integrated test system capable of operation at either a central or remote location, by a single individual, to permit identification of digital data circuit faults in the nature of either transmission faults or protocol faults and diagnosis of problems. It should also be pointed out that certain types of faults may be more readily identified as one type of fault in view of the results of other types of tests. For example, the results of certain protocol testing may aid in the diagnosis of physical faults and vice versa. However, in the absence of an integrated physical/protocol capable test system as herein described, the benefits of such interactive testing have not been obtainable.
It is therefore an object of the present invention to provide improved systems and methods for testing digital data transmission circuits which provide combined capabilities of transmission and protocol testing.
It is a further object of the invention to provide such test systems and methods enabling the diagnosis of faults based on the results of selected transmission and/or protocol testing of selected transmission circuits, and such test systems adapted to provide to the user suggestions as to probable cause of faults based on analysis of such results of selected transmission and/or protocol testing. It is also an object to provide such systems and methods whereby the results of such analysis are automatically used to determine the desirability of, and to appropriately cause the performance of, additional tests whose results are then used for performing additional fault analysis.
It is a further object of the invention to provide such test systems and methods enabling the recording and retention of benchmark test data representing acceptable operation of a transmission circuit and subsequent use of such benchmark data in the diagnosis of faults.
It is an additional object of the invention to provide transmission circuit test systems and methods which may be remotely accessed and controlled via a terminal at a customer facility, to permit selection, implementation and evaluation of transmission and/or protocol testing directly by customer personnel.